As known, a controller is used in a decorative light sets to control each light set to twinkle independently. A known electric circuit of the controller is shown in FIG. 1. It is understood that each electric wire 5 of the light sets must be connected with an IC board 4. In prior art, the wires 4 are welded to the IC board 4. As a result, a producer must produce the IC board 4 first and then sends them to the light-set department. After welding electric wires on the IC board, the assembly is placed in a box to form a controller. In such procedure, we find that it raises the rate of damage during transportation and limits the produced amount because of the serial manufacturing. Another drawback occurs since the strength of the welding is not enough. The electric wires are possibly separated from the IC board during assembling and the light sets will be out of work.